Before beginning the recipe, prepare all of the ingredients. Reserve any scraps, including onion and garlic paper, the tops and bottoms of the bell peppers, and any root ends from the scallions and celery for the homemade stock. First, peel and dice the onion. Next, trim and slice the celery. Next, trim, deseed, and dice the bell peppers. Transfer the diced onion, peppers, and celery to a large bowl. Trim and mince the scallions and separate the white and green parts. Next, peel and mince the garlic cloves. Keep the white parts of the scallions and the minced garlic together in a bowl. Reserve the green parts of the scallion for serving.

Add the flour and oil to a large, heavy-bottomed stockpot and turn the heat to medium. Cook, whisking or stirring regularly, for 20–30 minutes until the roux reaches the color of peanut butter. Next, turn the heat to low and continue stirring for an additional 20–30 minutes until the roux reaches the color of a copper penny.

Melt the butter into a second large pot. Add the reserved shrimp shells and cook in the hot butter for 1 minute. Add the reserved prep scraps and cover with 8 cups of water and a generous sprinkle of salt. Bring to a boil and then reduce heat and simmer as the roux cooks.

Once the roux finishes cooking, add the onion, celery, and bell peppers and turn the heat to medium-high. Stir to coat the vegetables with the roux and cook for 5 minutes.

Add the garlic and white parts of the scallions and cook for 1 minute more. Season lightly with salt and pepper. Add the Creole seasoning and cayenne powder if using.

Strain the stock through a sieve into a large bowl. Using a ladle, add a few ladles of the stock to the roux and whisk to incorporate. Continue ladling the stock, whisking after each addition, until all the stock has been added—taste and season to your preferences. Bring to a boil and then reduce heat and simmer for an hour until the vegetables are tender. Taste and season once more. Skim off any foam that floats to the top of the gumbo.

Add the shrimp and andouille sausage to the pot and cook for 5–10 minutes until the shrimp are opaque and cooked through. Taste and season once more.

Serve the gumbo with cooked white rice and garnish with the green parts of the scallions. Sprinkle with gumbo filé and enjoy!